Using git with ssh-agent on Windows

I'm on Windows. I installed git and posh-git (some helpers for Windows PowerShell). I can add keys with ssh-add and can authenticate with github and my webserver. I can also use git from the PowerShell to interact with my repositories.

But there is one thing I can't do: I use git-plus for the Atom editor. And I don't get it to push to my repo. What is my problem?